The bait is a grain of corn attached to one end of a thread; the other
end operates the camera shutter; but the pose is almost “studied”.]
After rodents become enormously abundant, if food becomes scarce
they sometimes make extended migrations, during which vast numbers
swarm across the country, like the lemmings of the North or the gray
squirrels during their historic migrations of early days in the eastern
United States. At such times vast numbers of the wandering hordes
perish; epidemic disease also plays its part in reducing their numbers.
Nature thus is self-limiting in restraining the permanent increase of
any species beyond the numbers needed to preserve its balance.
The advent of man in new regions with his clearing of forests,
cultivation of the soil, and destruction of animal life for food or
other purposes, quickly upsets the balance of nature, and some species
are much reduced in numbers or disappear, while others, especially
among the smaller kinds of mammals, may greatly benefit through added
food supplies, and then increase until they become a pest, to be
destroyed by the farmer as a measure of self-protection.